1. Field of The Invention
The present invention relates, in general, to sealed, expandable containers and, more specifically, to gas containers formed of multiple sheet layers.
2. Description of the Art
Expandable sealed containers or bags are employed in numerous applications, such as for collecting and temporarily storing gas emissions for motor vehicles before the collected emissions are analyzed by test equipment. Such containers are expandable to a constant volume to collect a known quantity of gaseous emissions.
Such expandable containers typically include a fitting sealingly mounted through one sidewall which is connectable to an external gas source and discharge device for receiving external gases and for discharging such gases from the container. The fitting directs the gas into the container for storage as well as allowing the stored gas to be completely evacuated from the container. The fitting and the sealed container are typically made of an inert material, such as a fluorinated carbon plastic sold under the registered trademarks TEFLON and TEDLAR.
In constructing such an expandable container, single thickness or ply sheets are overlaid on each other and sealingly connected at their peripheral edges by a conventional heat seam or seal.
TEDLAR polyvinyl fluoride film (PVF) is ideally suited for a number of applications due to its resistance to many chemicals, ultraviolet radiation, etc. In expandable container applications, polyvinyl fluoride film is used in a surface characteristic allowing heat sealing. Other formulations of TEDLAR polyvinyl fluoride film cannot be heat sealed. TEDLAR polyvinyl fluoride film is available in at least two formulations labeled "A" TEDLAR and "B" TEDLAR. "B" TEDLAR is treated on both side surfaces to enable adhesive to adhere to the sheet thereby permitting the bonding of the polyvinyl fluoride film or sheet to another sheet or material layer. For example, TEDLAR PVF film is laminated by an adhesive to flexible and reinforced vinyl fabrics for a number of indoor and outdoor applications including signs, awnings, and protective covers. The fabric or filaments are typically disposed inside of the PVF material layers to provide strength and stability to the material stock. The PVF film is disposed outermost over the vinyl fabric for ultraviolet protection and easy cleanup.
However, "B" TEDLAR which is treated on both surfaces for receiving adhesive is not heat sealable thereby preventing the use of this material in expandable bags formed of multiple sheets which are heat sealed at their peripheral edges. "A" TEDLAR PVF film has only one surface treated for receiving an adhesive. The other surface is "strippable" so as to be heat sealable to like "A" TEDLAR PVF films. Thus, it would be desirable to provide a sealed, expandable container which makes use of the advantages of a multiple ply stack of polyvinyl fluoride film and other materials while at the same time being easily heat sealable to form a sealed interior container. It would also be desirable to provide a sealed container formed of multiple ply sheets in which at least one sheet is a polyvinyl fluoride film and the at least one other sheet is a flexible vinyl.
In certain applications, the noise generated by the crinkling of the expandable container as it expands and contracts is objectional. Thus, it would be desirable to provide an expandable sealed container which is constructed to generate less objectional noise during expansion and contraction of the container.